/**
 * ─────────────────────────────────────────────
 *  SPB Drive — Personal Cloud Drive
 * ─────────────────────────────────────────────
 *  Author  : Simon-Pierre Boucher
 *  Contact : contact@spboucher.ai
 *  File    : src/preview/code.mjs
 *  Purpose : Shiki syntax highlighting + markdown-it GFM rendering
 *  License : MIT © Simon-Pierre Boucher
 * ─────────────────────────────────────────────
 */

import { createHighlighter } from 'shiki';
import MarkdownIt from 'markdown-it';
import anchor from 'markdown-it-anchor';
import taskLists from 'markdown-it-task-lists';

/** Extension → shiki language id. Anything unknown highlights as plaintext. */
export const EXT_LANG = {
  js: 'javascript', mjs: 'javascript', cjs: 'javascript', jsx: 'jsx',
  ts: 'typescript', tsx: 'tsx', py: 'python', rb: 'ruby', go: 'go', rs: 'rust',
  c: 'c', h: 'c', cpp: 'cpp', cc: 'cpp', hpp: 'cpp', cs: 'csharp', java: 'java',
  kt: 'kotlin', swift: 'swift', m: 'objective-c', php: 'php', sh: 'shellscript',
  bash: 'shellscript', zsh: 'shellscript', fish: 'fish', ps1: 'powershell',
  sql: 'sql', html: 'html', htm: 'html', xml: 'xml', css: 'css', scss: 'scss',
  less: 'less', json: 'json', jsonc: 'jsonc', yaml: 'yaml', yml: 'yaml',
  toml: 'toml', ini: 'ini', conf: 'ini', env: 'ini', dockerfile: 'docker',
  makefile: 'make', mk: 'make', cmake: 'cmake', gradle: 'groovy', groovy: 'groovy',
  lua: 'lua', r: 'r', jl: 'julia', scala: 'scala', pl: 'perl', ex: 'elixir',
  exs: 'elixir', erl: 'erlang', hs: 'haskell', ml: 'ocaml', clj: 'clojure',
  vue: 'vue', svelte: 'svelte', astro: 'astro', graphql: 'graphql', gql: 'graphql',
  proto: 'proto', tf: 'hcl', hcl: 'hcl', nix: 'nix', zig: 'zig', dart: 'dart',
  sol: 'solidity', asm: 'asm', s: 'asm', vim: 'viml', diff: 'diff', patch: 'diff',
  tex: 'latex', bib: 'latex', md: 'markdown', njk: 'html', csv: 'csv', tsv: 'tsv',
  txt: 'plaintext', log: 'log', bat: 'bat', cmd: 'bat', vb: 'vb', fs: 'fsharp',
  nim: 'nim', cr: 'crystal', d: 'd', pas: 'pascal', f90: 'fortran-free-form',
  cob: 'cobol', ada: 'ada', prisma: 'prisma', cue: 'cue', http: 'http',
};

let highlighterPromise = null;

async function getHighlighter() {
  if (!highlighterPromise) {
    highlighterPromise = createHighlighter({
      themes: ['dark-plus', 'light-plus'],
      langs: ['javascript', 'typescript', 'python', 'json', 'yaml', 'markdown', 'shellscript', 'html', 'css', 'sql'],
    });
  }
  return highlighterPromise;
}

/** Resolve a shiki language for a filename (plaintext fallback). */
export function langForFile(name) {
  const base = name.toLowerCase();
  if (base === 'dockerfile') return 'docker';
  if (base === 'makefile') return 'make';
  const ext = base.includes('.') ? base.split('.').pop() : base;
  return EXT_LANG[ext] ?? 'plaintext';
}

/**
 * Highlight source text → themed HTML (dual theme via CSS variables).
 * Unknown or unloadable languages degrade to plaintext, never throw.
 */
export async function highlightCode(text, name, { maxBytes = 2_000_000 } = {}) {
  const clipped = text.length > maxBytes;
  const source = clipped ? text.slice(0, maxBytes) : text;
  const hl = await getHighlighter();
  let lang = langForFile(name);
  if (!hl.getLoadedLanguages().includes(lang)) {
    try {
      await hl.loadLanguage(lang);
    } catch {
      lang = 'plaintext';
    }
  }
  const html = hl.codeToHtml(source, {
    lang,
    themes: { dark: 'dark-plus', light: 'light-plus' },
    defaultColor: false,
  });
  return { html, lang, clipped };
}

const md = new MarkdownIt({ html: false, linkify: true, typographer: true })
  .use(anchor, { permalink: anchor.permalink.headerLink({ safariReaderFix: true }) })
  .use(taskLists, { enabled: false });

// Fenced code inside markdown gets a plain <pre> with a language class;
// mermaid fences are tagged for client-side rendering.
md.renderer.rules.fence = (tokens, idx) => {
  const token = tokens[idx];
  const info = (token.info || '').trim().split(/\s+/)[0];
  const escaped = md.utils.escapeHtml(token.content);
  if (info === 'mermaid') {
    return `<pre class="mermaid-block" data-mermaid>${escaped}</pre>\n`;
  }
  return `<pre class="code-fence"><code class="language-${md.utils.escapeHtml(info || 'text')}">${escaped}</code></pre>\n`;
};

/** Render GFM markdown → sanitized HTML (raw HTML disabled). */
export function renderMarkdown(text) {
  return md.render(text ?? '');
}